Subject: Avoiding the Desire to Collimate Your Maksutov
Sent: Wednesday, August 8, 2001 18:14:12
From: sherrodc@ipa.net (Clay Sherrod)
All of the recent flurry of activity and "concern" regarding whether or
not each of our ETX scopes is in precise collimation has hit like a
wave. Hopefully this crest will be short-lived.
I DO NOT RECOMMEND OWNERS ATTEMPTING HOME COLLIMATION on a Maksutov. I
have said this many times. Indeed, there is a way to do it, but you
must keep in mind two things if you are tempted to change the
collimation of your Maksutov scope....this applies whether you have a
Meade or a Questar:
1) Even though an out-of-focus star image may appear to reveal that
your scope is out of collimation it does NOT mean that it necessarily is
(see my recent posting under the Tech Tips...."collimating a Mak...").
Indeed, most Maksutovs will show a slight "donut" offset when at either
side of focus, when the telescope is perfectly collimated IN FOCUS;
2) Collimation is now done with extremely precise machinery that is
computer generated for the optimum positioning of THREE (3) optical
elements in your system, not just the primary as has been discussed
tweaking here.
I do understand that some degree of success is possible through
collimating on a Christmas ball, but overall one of the most common
problems that I see results from self-collimating at home.
Ask yourself this question: When I tweaked the primary via the six
screws in the rear cell, did I also compensate the meniscus lens to
coincide with that change as you MUST in a Maksuktov? Once that
meniscus lens was then set, did I change the axial angle of the
secondary mirror to that of the corrector lens which I just arranged
precisely with the primary which is now "collimated" via my three screws
in the back of the telescope?
Nope, you did not and cannot.
Please do not tamper with your collimation; if you have reason to
believe that it is far out, do the in-focus star test as I have
described under: http://www.weasner.com/etx/techtips/collimating.html
and do it carefully and objectively. If, after doing this test you still
feel that your scope is not performing up to par, then by all means let
Meade do it for you....they have the equipment to answer "yes" to the
above....you do not.
Most telescope owner suffers from "instrument hypochondria" in that he
or she hears about another owner's scope that was in poor collimation
and suddenly.....I'VE GOT THAT TOO!! In reality, the telescope has been
giving nights, weeks, months....years, of excellent service and views.
Suddenly, because the subject has been brought up, yours is suffering
too!
Please heed this advice....something are left better off alone. You
will be much happier in this instance if you do.
P. Clay Sherrod
Arkansas Sky Observatory